1. Field of the Invention
This invention relates to a system for the production of duplicate copies of images. The invention is particularly concerned with duplicators of the type wherein copy sheets can be imaged on both sides while being supported by a single carrier, for example, an impression cyclinder.
Since copy sheet material of the type conventionally employed can readily accept images on both sides, it is highly desirable to provide equipment suitable for transferring images to both sides of a copy sheet. This provides clear savings in the amount of paper employed, additional savings in the amount of space occupied by the copies produced, savings in production time, and savings in cost of equipment.
2. Description of the Prior Art
Various systems have been developed to produce copy sheets imaged on both sides (hereinafter referred to as "duplexing"). Some systems, including Stonemetz U.S. Pat. No. 252,153, teach means for duplexing copies wherein a sheet is introduced between an impression cylinder and a type cylinder. In that system, the type cylinder carries two forms for transferring separate images, and a "blank" area is defined between the forms. The type cylinder makes one revolution while the smaller impression cylinder makes three revolutions. The copy sheet is printed on one side during a first revolution of the impression cylinder and discharged from the equipment. The impression cylinder makes an additional revolution while the "blank" area of the type cylinder passes, and the copy sheet is then re-fed, trailing edge first, for formation of the other image on the other side of the copy sheet during the third revolution of the impression cylinder.
Zahradnik application Ser. No. 858,606, filed on Dec. 7, 1977, entitled "Staging Mechanism For Duplexing Copy Machines" and Borneman applications Ser. No. 826,847, filed on Aug. 22, 1977, now U.S. Pat. No. 4,186,662, entitled "Duplexing Copying System", and Ser. No. 931,522, filed on Aug. 7, 1978, entitled "Duplexing Copying System" (The subject application and each of these applications being commonly assigned) disclose highly efficient means for achieving duplexing of copy sheets. These systems in particular provide means for delivering a copy sheet to an impression cylinder with the first image being transferred to one side of the sheet. Reversing means are associated with these constructions whereby the sheets are re-fed to the impression cylinder, trailing edge first. The impression cylinder then carries the sheets past image transfer means whereby an image is formed on the opposite side of each sheet.
First grippers employed with the respective impression cylinders engage the leading edge of each sheet fed to the impression cylinders. Each system also includes a second gripper which is involved in the reversing operation, the second gripper engaging the trailing edge of each sheet to achieve the second side image transfer.
In the case of the Zahradnik and first-filed Borneman applications, the systems include reversing stations which receive sheets after they are released by a first gripper. These reversing stations include mechanisms for re-feeding the sheets toward the second grippers whereby the formerly trailing edge of these sheets is engaged by the second grippers.
In the case of the latter-filed Borneman application, a continuation-in-part of the first-filed Borneman application, the second gripper incorporates separate gripper means with one gripper means engaging the trailing edge of each sheet as this trailing edge is first brought onto the impression cylinder. After release of the sheet by the first gripper, the second gripper is adapted to turn through 180.degree. whereby the second gripper achieves re-feeding of the sheet to the impression cylinder without releasing the trailing edge.
Prior art statements submitted with the above entitled applications are hereby incorporated by reference.